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New stink bug control guide developed

Stink bugs come in three distinct flavors in the Southeast — all of them a problem for growers. A hot-off-the-press guide sponsored by Cotton Incorporated will give growers the latest management tools for dealing with these pests.

The publication, “Managing Stink Bugs in Cotton: Research in the Southeast Region”, is a compilation of over three years of research findings by entomologists from Virginia, the Carolinas, Georgia, and Alabama. This large research effort was sponsored by state cotton support committees, Cotton Incorporated, and the Southern Region IPM Center.

Ames Herbert, a professor and entomologist at Virginia Tech, says, “This publication is the culmination of a 3-year effort by the co-authors and presents new thresholds and scouting procedures.”

The publication will be available in limited supply to growers, crop consultants and Extension agents in the Southeast. It will also be posted on Web sites by each university researcher involved in the studies that led to the publication.

The new publication deals with stink bugs in cotton. However these tiny pests also damage soybeans, corn and other crops grown in the Southeast. As growers, across all crops depend more and more on genetic inclusion of Bacillus thuringiensis (Bt) and other naturally occurring toxins into seed, they rightfully so will be applying less and less contact insecticide.

These new multi-stacked varieties will be a blessing for both growers and stink bugs that are not affected by the toxins. Finding economical, efficient, and environmental friendly means of controlling stink bugs has been an ongoing challenge for entomologists for the past several years.

Stink bugs are likely to be a bigger problem in the future than they have been in the past on cotton, says Clemson University Entomologist Jeremy Greene. The new Widestrike and Bollgard II varieties that are replacing Triple Nickel and other popular cotton varieties containing the single Bt trait are much more efficient in controlling bollworms and a number of other worm pests of cotton.

With little need for contact insecticides to bolster built-in genetic control of bollworms, growers are likely to spray less and less insecticide to control worm pests. The organophosphate (OP) and synthetic pyrethroid (SP) insecticides that were used for backup on bollworm control had a secondary value of knocking out stink bugs.

With less insecticide going out, cotton, entomologists across the Southeast are concerned that stink bug will become the No. 1 pest for growers to manage.

Finding precise thresholds at which stink bugs should be sprayed is an ongoing challenge made more difficult because all stink bugs are not alike and the different species prefer different host crops, have different biological traits and respond differently to insecticides.

The primary stink bug species that attack cotton in the Southeast are the brown stink bug, the green stink bug and the southern green stink bug. In Virginia and North Carolina green and brown stink bug are the predominant pests.

Herbert says though these two species are related, they are very different in how they impact cotton and other crops. One prefers woods and high growing vegetation and the other prefers grasses. Knowing which species is in a field is critical to knowing how to manage it in the most cost-efficient way.

In Georgia the primary stink bugs are the southern green and brown stink bug. In South Carolina all three species are common.

Cotton planted adjacent to woodlands versus grasslands is likely to have different stink bug populations. Likewise, cotton planted adjacent to peanuts or soybeans is likely to have more boll damage, more fiber quality loss and overall less lint value because of stink bug damage.

How to kill stink bugs has not been an issue since these insects re-emerged as a major pest of cotton — a number of OP and SP insecticides will do the trick. Knowing when to spray to achieve maximum control, minimum cost and minimum environmental risk is a big problem.

The new management guide gives growers some valuable insights on these critical management options. In three years of testing in North Carolina and Georgia there was a dramatic difference in yield and subsequently on crop value based on when a combination OP and SP was sprayed on cotton.

When applied too early — one to four weeks after first bloom, yield dropped from 5 percent to 6 percent. When sprayed too late — more than six weeks after first bloom — the damage was done, with yield losses nearing 25 percent. Spraying 3-4 weeks after bloom increased yield by 10 percent.

By far the most optimum time to spray OPs and/or SPs, based on the North Carolina and Georgia tests was from 4-5 weeks after first bloom. Using this timely spray, researchers recorded an increase of nearly 60 percent yield over non-treated check plots.

Herbert, who was one of the team that was instrumental in getting the stink bug publication done, says the new guide offers growers in the Southeast a succinct summary of the best research data available to help them manage stink bugs in cotton over the next few years.